JSON parsers are not really slow. JSON is simple enough that allows multiple implementations for parsers and easy adoption. But HJSON additions have some serial

JSON parsers are not really slow. JSON is simple enough that allows multiple implementations for parsers and easy adoption. But HJSON additions have some serialization cost overhead. Because of this eventually you will need to convert your HJSON to JSON prior to deploying, and that would make things slower. You will be dealing with 2 formats instead of one. Then, do you really believe that adding all this syntactic "features" (overhead) will make it less error prone? It will make it more error prone because it has more things to consider!